Add setq special form

src/main.c

@@ -16,6 +16,7 @@ int main(int argc, const char **argv) {
     ucl_state_put(state, "let", ucl_special_create(ucl_special_let));
     ucl_state_put(state, "if", ucl_special_create(ucl_special_if));
     ucl_state_put(state, "defun", ucl_special_create(ucl_special_defun));
+    ucl_state_put(state, "setq", ucl_special_create(ucl_special_setq));
 
     ucl_state_put(state, "print", ucl_builtin_create(ucl_builtin_print));
     ucl_state_put(state, "list", ucl_builtin_create(ucl_builtin_list));